1. Field of the Invention
Example embodiments relate in general to a method and apparatus for the monitoring of power readings and the calibration of neutron flux monitors in a nuclear reactor core, using Transverse In-Core Probes (TIP).
2. Related Art
A typical nuclear power plant includes neutron flux monitors, such as local power range monitors (LPRMs), which monitor neutron flux at many discrete points throughout the reactor. This information may be processed by core monitor software that determines the 3-Dimensional (3D) nodal powers used in monitoring, controlling and modeling reactor power levels. While LPRMs may accurately measure neutron flux, over time these instruments lose sensitivity at different rates, such that the gain electronics of these instruments must be individually recalibrated. A transverse in-core probe (TIP) system may be used in this recalibration process.
Conventionally, a TIP system includes a TIP detector attached to a TIP cable that is mechanically moved in and out of a nuclear reactor core, through dry tubes or other types of instrument tubes. Conventionally, instrument tubes house the LPRMs, and the instrument tubes allow the TIP cable to be drawn through the tube such that the TIP detector may be positioned directly next to the LPRM which is being calibrated. TIPs may take gamma flux readings, and these readings may be recorded at about every axial inch of cable movement, as the cable moves through the instrument tube. Conventionally, TIP detector gamma flux readings are taken at axial elevations throughout the core, and these readings are used to calibrate the LPRMs located at known axial and radial locations throughout the reactor core. This calibration of LPRMs may need to be repeated on a continual basis, every 60 days, or as otherwise determined by a plant maintenance schedule.
However, a concern that the exact location of a TIP detector is not known exists, because as TIP cables become compressed or worn overtime and as the cable is expelled through tortuous and long pathways throughout the reactor core, the exact length of the cable and the subsequent exact location of the TIP detector located on the TIP cable becomes uncertain. A recalibration of the LPRMs based on TIP detector readings that may be out-of-place can create inaccuracies in LPRM readings, which may affect the accurate control and monitoring of power levels in the core.